"One man," says Boris Johnson, "can make all the difference." But Johnson, who was recently given odds of 5/1 to be the next Tory leader, isn't talking about himself – instead, he's referring to Winston Churchill, whom he describes as "the resounding human rebuttal to all Marxist historians", and the subject of the book he has just been commissioned to write.

Johnson is finding time in his busy schedule as London mayor to pen the title on "the character, life, legacy and meaning today" of Churchill, said publisher Hodder & Stoughton, describing the combination as "the perfect match of author and subject". Rupert Lancaster, who acquired the book for Hodder, said that Johnson "combines scholarship, passion and objectivity – and whatever he writes is supremely readable".

Johnson said that his latest project was inspired because he is "interested in the memory of Churchill, and how it has been distorted". The book is provisionally entitled The Churchill Factor, and will be published next autumn.

"I want to shine a light on some aspects of Churchill's character and to explain how Churchill made a difference to events or to society – and explore his meaning and his message today," said Johnson. "He is the resounding human rebuttal to all Marxist historians who think history is the story of vast and impersonal economic forces. The point of the 'Churchill Factor' is that one man can make all the difference."